1. Field of the Invention
The invention is directed to a method and apparatus for monitoring a winding hardness of a material web wound onto a winding roll.
2. Discussion of Background Information
The present invention will be described below with respect to a material web, such as, for example, a paper web. However, it is understood that the invention is equally applicable to other types of web material without departing from the spirit and/or scope of the invention.
During an operation to produce a material web, such as, for example, paper web, the paper web is typically wound into saleable rolls, referred to as winding rolls. Generally, the paper web is wound onto a core, such as, for example, a cardboard tube. During this operation, it is desirable to achieve a winding hardness pattern in which the winding hardness decreases from a center to an outside.
Factors that influence a winding hardness include, but are not limited to, for example, a pressure with which the paper web is pressed against the winding roll, when the paper web encounters the winding roll, and a tensile stress wound into the paper web. In this regard, it is noted that the tensile stress can be changed (varied) by, for example, changing a driving torque (e.g., increasing or decreasing the driving torque) of an associated winding motor that forms the winding roll. In a king roll winder, in which the winding roll lies in a winding bed formed by a plurality of king rolls, a wound-in tensile stress can be changed by operating one drum winder, of a plurality of drum winders, at a speed (or torque) that differs from the speed (or torque) of the remaining drum winders.
Experience with winding rolls has yielded values that can be used to influence the winding hardness in a desired direction. However, it is very difficult to actually determine the winding hardness during a winding operation.